Milling wheel structure

ABSTRACT

A milling wheel structure for a milling machine comprising a circumferential row of interchangeable cartridges which are nonsymmetrically spaced on the periphery of the wheel. The cartridges receive disposable multiedge cutters, which are rotatable to bring other edges into cutting relation. The cutters are of the finishing or semifinishing type, both of which may be used simultaneously or individually.

United Swen atet Kilbonrne et ml.

4 Fell, 2.32., 1972 MILLING WHEEL STRUCTURE Inventors: Ralph WernerKillbnurne, Glenn Mills; Frank L. Di Ferdlnandlo, West Chester, both ofPa.

Westinghouse Electric (Importation, Pittsburgh, Pa.

Filed: Dec. 8, 1969 Appl, No: 883,015

Assignee:

ILLS. Cl ..29/105, 29/97 Int. Cl. ..lB26d 1/00, 826d 1/12 FieldofSearclh ..29/103, 105, 103 A, 105 A,

References Cited UNITED STATES PATENTS Graves et a1. ..29/ 105 A3,203,072 8/1965 Careje ..29/105 A 1,460,030 6/1923 Mattson ..29/105 A2,645,003 7/1953 Thompson et al. .....29/l05 3,200,474 8/1965 Kvalowetzr ..29/ 105 3,175,276 3/1965 Weber et a1. ..29/105 PrimaryExaminerHarrison L. l-linson Attorney -A. T. Stratton, F. P. Lyle and F,Cristiano. Jr.

[57] all Till/11:11

A milling wheel structure for a milling machine cmnprising ncircumferential row of interchangeable cartridges which arenonsymmetrically spaced on the periphery of the wheel. The cartridgesreceive disposable multiedge cutters, which are rotatable to bring otheredges into cutting relation. The cutters are of the finishing orsemifinishing type, both of which may be used simultaneously orindividually.

6 Claims, 9 Drawing Figures PATENTEDFEB 2 2 I972 SHEET 1 OF a INVENTORSKnboumwr Ralph Werner WITNESSES Frank L. DlFerdinundo PATENIED FEB 2 2I972 SHEET 0F Q PEG. 4

MILLING WHEEL STRUCTURE BACKGROUND OF THE INVENTION The followingdisclosure relates to milling machines and more particularly to arotatable milling wheel structure.

One of the major problems in milling, where large workpieces such asturbine casings are to be milled is that severe vibrations occur on theworkpieces as the cutters on the rotating wheel come in contact with theworkpieces. These vibrations limit the rate of feed of the workpieces orthe speed at which the wheel traverse the workpieces. Furthermore, thevibrations and the kind of metal to be milled limit the types and gradesof material used as milling cutters.

Large turbine casings are now very large and will be even larger in thefuture. For example, turbine casing halves made of low carbon steelsweigh approximately 52 tons and require extensive, time consumingfinishing machining operations. Furthermore, the finishing of theturbine casings requires extremely close machining tolerances. As harderand more brittle cutter material is used for finer finishes and closertolerances, there is a corresponding increase in cutter failures. On theother hand, as the cutter materials become less hard, there is acorresponding increase in wearing and chipping of the cutters. Thisresults in more rapid cutter replacement, the limiting of obtainabletolerances, and the restricting of the quality of finishes available.Previously, the hardest commercially usable material in milling cuttersfor large fabrications of low carbon steels was tungsten carbide.Titanium carbide cutters, for example, proved too brittle.

Another problem common to the conventional milling process is that theworn milling cutters are often reground and used again. The grindingprocess is time consuming and expensive. Furthermore, it is necessary todetermine the amount the cutter was reduced so that the cutter can bereplaced in the wheel at a constant preset cutting distance. This isnecessary to maintain a precision, numerically controlled millingprocess.

A still further problem is that large fabrications are first roughmachined," semifinished" in a second operation and are finally finishmachined" in a third operation. This results in considerable time andexpense to perform three operations individually and to convert andreconvert from one operation to another.

It would be desirable then, to design a milling cutter that wouldminimize the vibrations of the workpiece, thereby increasing the rate offeed and enable the use of a harder material for the cutters. It wouldfurther be desirable to use a multisided, disposable cutter that couldbe easily and economically replaced. Furthermore, it would be desirableto perform the semi-finishing and the finishing operationssimultaneously. When it is necessary to perform these operationsindividually, it would be desirable to be able to readily convert fromone operation to another.

SUMMARY OF THE INVENTION The invention comprises a cylindrical wheelstructure for a milling machine. The wheel has radially extendingfingers, integral therewith, defining slots nonsymmetrically spacedcircumferentially on its peripherally. Firmly secured in the slots is acorresponding number of interchangeable cartridges extending axially.Disposable cutters are fastened to the cartridges. The cutters projectaxially beyond a face of the wheel to some predetermined degree.

In the preferred embodiment each cartridge has two preset, pre-shaped,side-by-side openings which accept two corresponding preshaped cutters;the radially outward cutter on the cartridge is of the semifinishingtype and the radially inward cutter is ofthe finishing type.

The second embodiment is similar to the preferred except that eachcartridge has only one cutter of the finishing type on the radiallyoutward portion of the cutter.

The cutters have multiple edges so that, upon wearing, the cutters arerotatable to bring outer edges into cutting relation. After all edgesare worn, the old cutters are removed and replaced with new cutters.

The cartridges and cutters are nonsymmetrically spaced peripherally soas to minimize vibrations and to enable the use of harder steel cutters.This has the advantages of permitting an increased rate of feed of theworkpiece without damage to the cutters or workpiece, prolonging thelife of the cutters, obtaining closer tolerances, and providing finerfinishes. Since the cutters are rotatable, have multiple edges, and aredisposable, these features provide cutters that can be easily andeconomically replaced while eliminating the need for grinding thecutters. The cartridges may be capable of holding two different types ofcutters and can perform both the semifinishing and finishing operationssimultaneously. Finally, since the cartridges are interchangeable, thetime for converting from one operation to another is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of aworkpiece being milled by a machine having a milling wheel structureformed in accordance with the present invention;

FIG. 2 is an enlarged plan view of a portion of the milling wheelstructure shown in FIG. 1;

FIG. 3 is a developed schematic view on a smaller scale than FIG. 2showing a peripheral view of the milling wheel structure;

FIG. 4 is a fragmentary view partially in section and partially inelevation taken approximately along line VV in FIG. 8 and showing a viewof a cutter cartridge;

FIG. 5 is an exploded view of one of the cutter cartridges;

FIG. 6 and 7 are side elevational views of the cutters employed in thecartridges;

FIG. 8 is an enlarged fragmentary view taken along line IV-IV in FIG. 2showing one of the cutter cartridges; and

FIG. 9 is an elevational view on the same scale as FIG. 4 of anothercutter cartridge.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, there isshown a representative milling machine 10 having a vertically extendingshaft 11 rotatable in the direction indicated by arrow (0 (although theshaft could also be extended horizontally). A circular milling wheelstructure I2 embodying the invention is secured to the shaft II. Thewheel structure I2 and the shaft 11 have been greatly enlarged forclarity because of their small sizes relative to the size of the millingmachine 10. The milling wheel structure 12 comprises a wheel 12a havinga central bore I3 (FIG. 2) mounted concentrically on the shaft II. On amachine bed I4 which may have ways I5 for guiding movement in adirection indicated by the arrow 2 is a workpiece I7 which as shown isone-half of an outer turbine casing. The milling machine 10 may move inany of three directions as indicated by arrows X, Y and Z. The workpieceI7 is shown being fed into the milling wheel structure 12, it beingunderstood that the milling machine 10, the bed I4, the shaft 11, andthe workpiece I7 comprise no part of the invention.

An enlarged plan view of the milling wheel structure I2 is shown in FIG.2, with one portion exploded for clarity. Extending radially outwardfrom the axis of rotation of the wheel R-R is a series of fingers I9which are integral with the wheel 12a. The fingers I9 define an annularrow of radially extending slots 21. The radially inward portions 23 ofthe slots 2ll and the radially outward portions 24 are at equal radialdistances from the axis of rotation R-R. The radially outward portions24 extend through the periphery of the wheel 12a. The slots 21 arepartially defined by leading wall portions 25 and trailing wall portion26. In a peripheral direction, the fingers 19 and slots 21 arenonsymmetrically spaced so that no two fingers or slots arediametrically opposite to each other. The slots 21 are approximatelyequal in size and similar in shape and the fingers 19 are similar inshape but circumferentially unequal in width.

On a 16-inch diameter wheel, fingers l9 and 21 have been employed toshow in FIG. 2, four representative angular spacings k, p, f, and a, toindicate the nonsymmetrical spacing arrangement. FIG. 3 shows adeveloped plan view of this milling wheel where the plan is divided intothree sections, A, B, and C, disposed in parallel relation one below theother and connected by dot-dash lines A-B and B-C indicating onecontinuous piece. The angular spacing arrangement is given in the tablebelow in radians and degrees where the alphabetical suffixes representthe angular spacing from reference lines L-L between the slots 21.

Spacing Radians Degrees a 0.3863 22 8 b 0.3427 19 38 7" c 0.3078 17' 38'8" d 0.2792 15 59 49" c 0.2554 I4 38' 00" f 0.2353 13 28' 54" g 0,250014 19' 16" h 0.272s is" 37' so" i 0.3000 17 11 I9" j 0.3332 l9 27" k0.3733 21 23' 19" 1 0.3527 20 I2 29" m 0.3158 18 5' 38" I1 0,2859 16 22'51" 0 0.2609 14 56 55" p 0.2399 13 44 47" q 0.2449 14 I 55" r 0.2668 |517' l2" 5 0.2928 16 46' 35" t 0.3243 18 48' l u 0.3632 20 48' 35" Asindicated in FIG. 2, four representative spacings have been shown. Forexample, referring to the above table, angular spacing k corresponds to0.3733 radians or 21 23'19p corresponds to 0.2399 radians or 13 4447",fcorresponds to 0.2353 radians or 13 28' 54" and a corresponds to0.3862 radians or 22 8 00''.

A plurality of cartridges 28 corresponding in number, size and shape tothe series of slots 21 are positioned to the slots. Fastening means areused to secure the cartridges 28 in the slots 21 and to allow for theminute adjustments necessary for precision milling.

As best seen in FIG. 2, the cartridges 28 are inserted in the slots 21,so the radially inward edges 42 of the cartridges 28 are in abutmentwith the wheel 12a at the radially inward portions 23 of the slots 21.The trailing faces 43 of the cartridges 28 fit into corresponding andcontoured surfaces in the trailing portions 26 of the fingers 19. Asbest seen in FIG. 4 and FIG. 5, two preformed and preshaped side-by-sideopenings 46 and 47 are on the leading face 49 near the top portion 50 ofeach cartridge 28. The opening near the radially outward edge 51 isapproximately circular in section to accommodate a rotatable, disposablecutter 53 frustoconically shaped.

As shown in FIG. 6, the frustoconical cutter 53 has a sloped wall 56 anda base 58, the wall and the base defining the edge 57 which is thecutting edge. Since the edge 57 is circularly continuous, only a portionof the edge is operative at any setting. Hence the cutter 53 may bedeemed to be multisided. As shown in FIG. 6, the wall 56 of the cutter53 is sloped at an angle a which is relative to a plane N-N normal tothe base 58 of the cutter.

Fastening means such as a screw 54 is placed through a hole in thecenter of each cutter 53 securing the cutter to the cartridge 28. Thecutter 53 projects slightly beyond the top portion 50 of the cartridge28 in an axial direction and slightly beyond the radially outward edgeSI. The base 58 makes an angle [3 of 10 with a radial plane P-P, bestseen in FIG. 2, which is a negative rake angle relative to therotational direction in of the wheel 12a. In the axial direction, thecutting base 58 makes an angle 6 of 5 with a plane going through therotational axis R-R', as shown in FIG. 8, which is a positive rake anglerelative to the rotation to of the wheel 12a. The cutting base 58 of thecutter 53 is inclined at an angle e of 10 with the leading face 49 ofthe cartridge 28 (FIG. 8).

The second preshaped opening 47 is located towards the radially inwardedge 42 of the cartridge 28 as shown in FIGS.

4 and 5. A plate 60 is secured to the leading face 49 of the cartridge28 by fastening means 61. The surface 63 of the plate 60 is accuratelymachined and provides a wall for the opening 47. The opening 47 isapproximately rectangular in section, with the top side removed andreceives a rotatable disposable cutter 64 which is approximatelyfrustopyramidically shaped.

As shown in FIG. 5, the frustopyramidically shaped cutter 64 has asquare base 68 having four sides 69 and a sloped wall 70. The four sides69 of the base 68 ofthe cutter 64 form four cutting edges. The twoopposite ends of each edge 69 are slightly tapered at an angle 1 whichis at 3 lead angle (FIG. 4) to minimize chatter and help preventchipping of the edges. Referring to FIG. 7 it can be seen that the wall70 of the frustopyramidical cutter 64 is inclined at an angle 6 of 20with a plane A-A normal to the base 68 of the cutter 64. The base 68 ofthe cutter 64 makes an angle B which is a 10 negative rake angle with aradial plane P-P relative to the rotational direction to of the wheel12a as shown in FIG. 2. The base 68 of the cutter 64 is inclined at anangle A which is a 15 positive axial rake angle with a plane goingthrough the axis of rotation R-R (FIG. 8). The base 68 of the cutter 64is flush with the leading face 49 of the cartridge 28. The cutter 64 ispositioned so that cutting edge 69 extends axially beyond the topportion 50 of the cartridge 28 best shown in FIG. 4. Fastening meanssuch as a screw 65 is inserted through a hole 66 in the center of eachcutter 64 into the cartridge 28 to secure the cutter to the cartridge.

As shown in FIG. 8, the fastening means comprise locking wedges 71a and71b, lift wedges 71c, and differential screws 72a, 72b, and 720.

The lock wedges 71b and the lift wedges 71c are inserted into the slots21 at a known distance from the bottom side 40 of the wheel 12a.Differential screws 72b are inserted radially inward through the lockwedges 71b, extending into the wheel 12a and locking the lift wedges 71cbetween the fingers 19 and the lock wedges 7 lb. Differential screws 720are inserted axially through the lift wedges 71c into the bottomportions 44 of the cartridges 28 to adjust the axial extension of thecartridges as best seen in FIG. 8. I

Lock wedges 71a are then inserted between the fingers 19 and thecartridges 28. Differential screws 72a extend radically inward throughthe wedges 71a into the wheel 12a locking the cartridges 28 to the wheeland preventing radial and axial movement, This type of wedge arrangementprovides each removal and installation of the cartridges 28 whileallowing for fine adjustments.

Because of the nonsymmetrical spacing of the cartridges in a peripheraldirection, the vibrational waves caused by the cutters hitting the metalat nonuniform time intervals cause damping and prevent resonance fromoccurring. This damping enables the use of harder cutters. For example,the cutters 53 which do the semifinishing operation can be made oftungsten carbide. The finishing cutters 64 can be made of titaniumcarbide. Since these cartridges 28 and cutters 58 and 64 perform bothsemifinishing and finishing operations, these are called combinationcutter cartridges.

The effects of reduced vibrations and harder cutters are the prolongingof the lives of the cutters, the increasing of the rate of feed of theworkpiece, and the obtaining of closer tolerances, resulting in finerfinishes. For example, tests using the new combination cutter cartridgeson low carbon steel fabrications have been conducted and the resultshave shown that at a linear feed rate of between 35 to 70 inches perminute, tolerances of 15-25 micro inches were obtainable percent of thetime. Under similar testing conditions in conventional millingprocesses, the maximum range of feed rate without damage to the cuttersor workpiece was 12 to inches per minute with tolerances of 80 to 125micro inches which were only dependable 60 percent of the time.

From the above, it can be seen that the maximum workable feed rateincreased from 20 inches per minute to 70 inches per minute or a 250percent increase; the tolerances were reduced on the low range from 80micro inches to 15 micro inches or a 81 percent decrease; and thedependability was increased from 60 percent to 80 percent or a 33percent increase.

The semifinishing cutters 53 being the radially outermost of the twocutters, first come in contact with the workpiece llll (FIG. 1). On theinitial passes, the semifinishing cutters 53 rough the workpiece andprepare it for the finishing cutters 64. On successive passes, the feedis increased and while the semifinishing cutters 53 are roughing a newportion of the workpiece, the finishing cutters 64 are working on theportions just semifinished. Both operations are then effectivelyperformed simultaneously, and approximately one-half the time ofperforming both operations individually is saved.

Additionally, the cutters 53 and 64 are multisided and rotatable abouttheir centers. Therefore, once preset distances for positioning thecutters 53 and 64 are determined, any new edges 57 and 69 of the cuttersafter rotation are at a known distance with no adjustments needed. Withthis type of arrangement, the cartridges 28 and cutters 53 and 64 can beset very accurately with a minimum of effort. The radial distance of thecartridges 28 is set by insertion of the cartridges into the formedslots 21. The axial distance 8 (FIG. 4) is set by measuring from thebottom side ofthe wheel 12 to the cutter edges 57 and 69 and can be setwithin 50 millionths of an inch by methods well known in the art becauseof the wedge arrangement previously discussed.

The semifinishing cutters 53 and the finishing cutters 64 are rotated atthe same time, but because the semifinishing cutters are rounded andhave more cutting edges, about one-half of the cutters 53 are used perfour sides of the finishing cutters 64.

After all edges 57 and 69 wear, the cutters 53 and 64 are removed fromthe cartridges 28. Previously, cutters were ground requiring a precisionprocess in which it was necessary to determine how much of the edgeswere removed from the cutting edge so the cutters could be properlyreset. Now the cutters 53 and 64 are disposed of and replaced. Nogrinding is required.

DESCRIPTION OF THE SECOND EMBODIMENT Referring to FIG. 9, a cartridge 73is shown which is employed in the same manner as cartridge 28 mounted ina wheel already described. This cartridge 73 is similar to cartridge 28but differs in the following. The cartridge 73 has a preformed andpreshaped opening 74 located on the leading face 75, toward the topportion 76, and, near the radially outward edge 77 of the cartridge 73.This cartridge 73 is called the finishing cartridge.

The openings 74 have two defining edges, one edge 79 being on thecartridge and the second edge 80 being precision ground on plate 81which is similar to plate 60 in the preferred embodiment. Finishingcutters 82 are secured to the cartridges 73, the cutters being similarto and interchangeable with the frustopyramidically shaped finishingcutters 64 in the preferred embodiment. The combination of the cartridge73 and the cutter 82 is called the finishing cutter cartridge.

The finishing cartridges 73 are dimensionally approximately equal to andinterchangeable with the combination cartridges 28 described in theprimary embodiment so that they can easily and economically replace thecombination cartridges 28 when switching from one operation to another.Additionally, in numerically controlled machines the interchangeabilityof the cartridges 28 and 73 gives the added flexibility necessary forminor adjustments.

The finishing cartridges 73 are used when it is necessary to mill arestricted area such as a corner or ledge ofa workpiece l7 (FIG. 1) towhich the finishing cutters 64 on the combination cartridges 28 cannotget.

Although more than one embodiment has been shown, it is intended thatall the matter contained in the foregoing description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense. For example, the finishing cutters 64 of the combinationcutter cartridges can be removed to form semifinishing cutter cartridgeswhich may be used when a semifinishing operation is only required.

What is claimed is:

II. In a rotatable milling wheel,

said wheel having radially extending fingers,

said fingers defining radially extending slots,

said fingers and slots being nonsymmetrically spaced in a peripheraldirection,

a series ofinterchangeable cartridges received in said slots,

said cartridges having leading faces and trailing faces,

each leading face having a pair of side-by-side,

preshaped openings,

half of said openings being on said leading face near the radially outeredge and top portion ofeach cartridge,

the other half of said openings being on said leading face near theradially inward edge and near the top portion on each cartridge,

a plurality of preshaped semifinishing cutters,

said semifinishing cutters being frustoconically shaped and havingmultiple edges,

a plurality ofpreshaped finishing cutters,

said finishing cutters being frustopyr'amidically shaped and havingmultiple edges,

said semifinishing cutters being secured to the corresponding preshapedradially outer openings,

said finishing cutters being secured to the radially inner openings, and

fastening means to secure said cartridges to said wheel.

2. In a rotatable milling wheel,

said wheel having radially fingers integral therewith,

said fingers defining radially extending slots,

said fingers and slots being nonsyrnmetrically spaced in a peripheraldirection,

a series of cartridges received in said slots,

each cartridge having at least one preset and preshaped opening,

a plurality of cutters,

said cutters having multiple cutting edges,

fastening means securing said cutters in said openings to saidcartridges,

fastening means to secure said cartridges to said wheel,

said cartridges being interchangeable with each other,

said cartridges having leading and trailing faces,

said leading faces having pairs of side-by-side, preset and preshapedopenings,

half of said openings being on said leading faces near the radiallyouter edges and the top portions of said cartridges,

the other half of said openings being on said leading faces near theradially inward edges of said cartridges, corresponding preshapedsemifinishing cutters secured to said radially outer openings,

and corresponding preshaped finishing cutters secured to said radiallyinner openings.

3. The structure defined in claim 2 wherein the seinifinishing cuttersare frustoconically shaped,

and the finishing cutters are frustopyramidically shaped.

4. In a rotatable milling wheel,

said wheel having radially extending fingers integral therewith,

said fingers defining radially extending slots,

said fingers and slots being nonsymmetrically spaced in a peripheraldirection,

a series ofcartridges received in said slots,

each cartridge having at least one preset and preshaped opening,

preset,

a plurality ofcutters,

said cutters having multiple cutting edges, fastening means securingsaid cutters in said openings to said cartridges,

fastening means to secure said cartridges to said wheel,

said cartridges being interchangeable with each other,

said cartridges having leading and trailing faces,

preset and preshaped openings on the leading faces near the radiallyouter edges and the to cartridges,

p portions of said finishing

1. In a rotatable milling wheel, said wheel having radially extendingfingers, said fingers defining radially extending slots, said fingersand slots being nonsymmetrically spaced in a peripheral direction, aseries of interchangeable cartridges received in said slots, saidcartridges having leading faces and trailing faces, each leading facehaving a pair of side-by-side, preset, preshaped openings, half of saidopenings being on said leading face near the radially outer edge and topportion of each cartridge, the other half of said openings being on saidleading face near the radially inward edge and near the top portion oneach cartridge, a plurality of preshaped semifinishing cutters, sAidsemifinishing cutters being frustoconically shaped and having multipleedges, a plurality of preshaped finishing cutters, said finishingcutters being frustopyramidically shaped and having multiple edges, saidsemifinishing cutters being secured to the corresponding preshapedradially outer openings, said finishing cutters being secured to theradially inner openings, and fastening means to secure said cartridgesto said wheel.
 2. In a rotatable milling wheel, said wheel havingradially fingers integral therewith, said fingers defining radiallyextending slots, said fingers and slots being nonsymmetrically spaced ina peripheral direction, a series of cartridges received in said slots,each cartridge having at least one preset and preshaped opening, aplurality of cutters, said cutters having multiple cutting edges,fastening means securing said cutters in said openings to saidcartridges, fastening means to secure said cartridges to said wheel,said cartridges being interchangeable with each other, said cartridgeshaving leading and trailing faces, said leading faces having pairs ofside-by-side, preset and preshaped openings, half of said openings beingon said leading faces near the radially outer edges and the top portionsof said cartridges, the other half of said openings being on saidleading faces near the radially inward edges of said cartridges,corresponding preshaped semifinishing cutters secured to said radiallyouter openings, and corresponding preshaped finishing cutters secured tosaid radially inner openings.
 3. The structure defined in claim 2wherein the semifinishing cutters are frustoconically shaped, and thefinishing cutters are frustopyramidically shaped.
 4. In a rotatablemilling wheel, said wheel having radially extending fingers integraltherewith, said fingers defining radially extending slots, said fingersand slots being nonsymmetrically spaced in a peripheral direction, aseries of cartridges received in said slots, each cartridge having atleast one preset and preshaped opening, a plurality of cutters, saidcutters having multiple cutting edges, fastening means securing saidcutters in said openings to said cartridges, fastening means to securesaid cartridges to said wheel, said cartridges being interchangeablewith each other, said cartridges having leading and trailing faces,preset and preshaped openings on the leading faces near the radiallyouter edges and the top portions of said finishing cartridges, aplurality of preshaped finishing cutters corresponding in shape to saidopenings, said cutters being disposed in said openings, and fasteningmeans to secure said cutters to said cartridges.
 5. The structuredefined in claim 4 wherein the cartridges extend outwardly in an axialdirection.
 6. The structure defined in claim 4 wherein the finishingcutters are frustopyrammidically shaped.